Dermatology Online Journal

Milker's callus
TP Vetrichevvel MD, C Udayashankar MD, P Oudeacoumar MD
Dermatology Online Journal 14 (7): 13

Department of Dermatology and STD, Aarupadai Veedu Medical College and Hospital (AVMC&H), Pondicherry, India. udayavmc@gmail.com

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Abstract

Calluses are a diffuse area of hyperkeratosis occurring as a normal physiological response to chronic, excessive pressure or friction on the skin. THey can be distinctive occupational stigmata when they occur on the hands. Herein we report the occurrence of calluses of the thumb in professional milkers as an occupational dermatosis.

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Introduction

Calluses are a broad-based or diffuse area of hyperkeratosis of relatively even thickness caused by repeated friction or pressure. They appear in predictable locations depending on activities, occupation, sports, and habits [1]. While callosities of the feet are usually a result of deformity, those of the hands are distinctive occupational stigmata [2]. Herein we describe a new observation of calluses of the hands induced by milking.

Case report

A 37-year-old man presented with a painless localized thickening on the back of both the thumbs for 9 years. It had started as an area of hyperpigmentation and thickening and had progressively increased in size over the years. There was no history of the appearance of pustules or discharge from the lesion and the other fingers were not involved. On physical examination, he had a single, nontender, hard, hyperpigmented, broad-based callus, 16 x 9 mm in size, with a rough, eroded surface on the dorsum of the interphalengeal joint of the left thumb (Fig. 1, two thumbs). It was freely mobile and there was no restriction of movement of the underlying joint. A similar 12 x 8 mm callus was seen on the right thumb in the same location. Interestingly, he also mentioned the occurrence of similar lesions in his colleagues at his workplace. He is a milker, engaged in the profession for the past 12 years. On average he milks 30 cows in 3 hours every morning and repeats the process in the evening. Histopathology of the lesion showed compact hyperkeratosis and acanthosis with moderate papillomatosis (Fig. 2). Later, on visiting his work place, we found that all of his colleagues engaged in the profession for more than 2 years had calluses varying in length from 7 to 24 mm, in the same location (Fig. 1). The diagnosis of milker's callus was confirmed by the similar clinical presentation and morphology in his professional colleagues. The patient was treated with paring followed by topical application of keratolytics.

Figure 1	Figure 2
Figure 1. Calluses located on the dorsum of interphalengeal joints of the thumb of milkers Figure 2. Histopathology of the lesion showing compact hyperkeratosis with moderate acanthosis

Discussion

Figure 3
Figure 3. Positioning of the thumbs during milking

Calluses arise from hyperkeratosis, a normal physiological response to chronic excessive pressure or friction on the skin. Friction can range from mild intermittent friction, producing lichenification and hyperpigmentation, to heavier and more persistent friction that produces callosities and nail damage [3]. Both pressure and friction play an etiological role in the development of milker's callus. During the process of manual milking the cow's teats are gripped between the dorsal aspect of the thumb, flexed at the interphalengeal joint and the palmar surface of the other fingers, exerting sufficient pressure along its length to express milk (Fig. 3). In professional milkers this process is repeated several times a day and over the years this frictional trauma produces this telltale sign. In response to friction, there is a steady rate of increase in epidermal turnover and accumulation of thickened, vertically oriented collagen bundles in the papillary dermis, resulting in lichenification and callus formation [2]. These effects of trauma can be further modified by humidity, sweating, age, sex, nutritional status, infection, genetic, and racial factors [4]. In our patients the morphology of the calluses were also modified by alterations in the grip technique when the big calluses interfered with milking.

Milker's nodule could be considered in the differential diagnosis. This is a zoonosis caused by parapox virus also occurs on the fingers. It usually presents as a reddish-blue, firm, slightly tender nodule that later crusts and resolves spontaneously without scaring in 4-6 weeks, usually without recurrence. Histologically, it is characterized by a multilocular vesicle in an acanthotic epidermis with intracytoplasmic inclusion bodies in the vacuolated epidermal cells; dilated capillaries and mononuclear cell infiltration is demonstrated in the dermis. Orf clinically and histopathologically resembles milker's nodules but is acquired from infected sheep and goats [5].

Occupational calluses have been described in professions involving mechanical trauma, such as tailors, gardeners, musicians, computer operators, and data-entry typists (mousing callous) [1, 6]. With increasing automation and less frequent manual operation of tools these occupational marks are bound to become less frequent, but ironically the use of machine milking and vacuum pressure devices have shifted the ill effects of mechanical trauma from the thumbs of milkers to the teats of cows who show higher incidence of rough teat end callosity (TEC) with longer machine-on time [7].

References

1. Goksugur N, Cakici H. A new computer-associated occupational skin disorder: Mousing callus. J Am Acad Dermatol 2006; 55(2):358-9.

2. Kennedy CT. Mechanical and thermal injury. In : Champion RH, Burton JL, Burns DA, Breathnach SM, editors. Rook/Wilkinson/Ebling Textbook of Dermatology. 6th edn. Oxford: Blackwell Science; 1998. p.890-908.

3. Adams RM. Occupational skin disease. In : Freedberg IM, Eisen AZ, Wolff K, Austen KF, Goldsmith LA, Katz SI, et al, editors. Fitzpatrick's Dermatology in general medicine. 5th ed. New York: McGraw-Hill; 1999.1609-20.

4. Kumari R, Thappa DM, Shivaswamy KN. Occupational marks in a coconut tree climber. Indian J Dermatol Venereol Leprol 2006; 72:311-312

5. Sterling JC. Virus infections. In: Burns T, Breathnach S, Cox N, Griffiths C, editors. Rook's Textbook of Dermatology. 7th edn. Oxford: Blackwell Science; 2004. p.25.1-25.83.

6. Kanerva L, Knuckle pads from boxing. European Journal of Dermatology 1998; 8 (5): 359-61

7. F. Neijenhuis, H. W. Barkema, H. Hogeveen, J.P. Noordhuize. Classification and Longitudinal Examination of Callused Teat Ends in Dairy Cows J Dairy Sci 2000; 83:2795-804.

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